Microbes are found virtually everywhere, often in high concentrations, and are responsible for a significant amount of disease and infection. Killing and/or eliminating these microorganisms is desirable for a variety of reasons.
Bacteria present special challenges because they can exist in a number of forms (e.g., planktonic, spore and biofilm) and their self preservation mechanisms make them extremely difficult to treat and/or eradicate. For example, the bacteria in biofilms or spores are down-regulated (sessile) and not actively dividing, which makes them resistant to attack by a large group of antibiotics and antimicrobials that attack the bacteria during the active parts of their lifecycle, e.g., cell division.
In a biofilm, bacteria interact with and adhere to surfaces and form colonies which facilitate continued growth. The bacteria produce exopolysaccharide (EPS) and/or extracellular-polysaccharide (ECPS) macromolecules that keep them attached to the surface and form a protective barrier effective against many forms of attack. Protection most likely can be attributed to the small diameter of the flow channels in the matrix, which restricts the size of molecules that can reach the underlying bacteria, and consumption of biocides through interactions with portions of the EPS/ECPS macromolecular matrix and bacterial secretions and waste products contained therein. (Certain fungi also can form biofilms, many of which present the same types of challenges presented here.)
Bacteria also can form spores, which are hard, non-permeable protein/polysaccharide shells or coatings. Spores provide additional resistance to eradication efforts by preventing attack from materials that are harmful to the bacteria.
Due to the protection afforded by a macromolecular matrix (biofilm) or shell (spore) and their down-regulated state, bacteria in these states are very difficult to treat. The types of biocides and antimicrobials effective in treating bacteria in this form are strongly acidic and/or oxidizing, often involving halogen atoms, oxygen atoms, or both. Common examples include hypochlorite solutions (e.g., bleach), phenolics, mineral acids (e.g., HCl), H2O2, and the like. Large dosages of such chemicals must be allowed to contact the biofilm or spore for extended amounts of time to be effective, which makes them impractical for many applications.
Recently developed formulations intended for use in connection with compromised animal/human tissue solvate a biofilm matrix so that still-living bacteria can be rinsed or otherwise removed from infected tissue; see, e.g., U.S. Pat. Nos. 7,976,873, 7,976,875, 7,993,675, etc. The concentrations of active ingredients in these formulations are too low to effectively kill the bacteria, however, thus making such formulations ill suited for use as surface disinfectants.
Neutral-to-very acidic disinfecting solutions that can disrupt macromolecular matrices, or bypass and/or disable their inherent defenses, allowing ingredients in the solutions to access the bacteria, attack cell membranes, and kill them have been described in U.S. Pat. Publ. No. 2010/0086576 A1.
Animal tissue wounds present both a good environment for bacterial, and even biofilm, growth and a surface or substrate requiring gentle treatment, thus making a difficult problem even worse.
Dental plaque, a biofilm that adheres to a tooth surface, consists of bacterial cells (mainly Streptococcus mutans and Streptococcus sanguis), salivary polymers and bacterial extracellular products. The accumulation of microorganisms subject the teeth and gingival tissues to high concentrations of bacterial metabolites, which results in widespread problems such as gingivitis and periodontal disease, including oral caries.
Nosocomial or hospital acquired infections (HAIs) can be caused by viral, bacterial, and/or fungal pathogens and can involve any system of the body. HAIs are a leading cause of patient deaths, and they increase the length of hospitalizations for patients, mortality and healthcare costs; in the developed world, they are estimated to occur in 5-10% of all hospitalizations, even higher for pediatric and neonatal patients. They often are associated with medical devices or blood product transfusions. Three major sites of HAIs are bloodstream, respiratory tract, and urinary tract. Most patients who have HAIs have invasive supportive measures such as central intravenous lines, mechanical ventilation, and catheters, which provide an ingress point for pathogenic organisms. Ventilator-associated pneumonia can be caused by Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), Candida albicans, Pseudomonas aeruginosa, Acinetobacter baumannii, Stenotrophomonas maltophilia, Clostridium difficile, and Tuberculosis, while other HAIs include urinary tract infections, pneumonia, gastroenteritis, vancomycin-resistant Enterococcus (VRE), and Legionellosis.
Medical equipment such as endoscopes, gastroscopes, the flow-channels of hematology and dialyzer equipment, the airflow path of respiratory equipment, ISE, HPLC, and certain catheters are designed to be used multiple times. Significant risks have been associated with inadequate or improper cleaning due to the presence of residual soil and/or improper disinfection or sterilization, up to and including HAIs from contaminated devices such as bronchoscopes contaminated with Mycobacterium tuberculosis and the transmission of Hepatitis C virus to patients during colonoscopy procedures.
Any surface that is or becomes moist is subject to biofilm formation. Thus, articles intended for permanent or temporary implantation—such as artificial hearts, stents, contact lenses, intrauterine devices, artificial joints, dental implants—are particularly susceptible. Extreme measures are taken to prevent biofilm formation because, once established, they are essentially impossible to eradicate in vivo and can cause life-altering, even lethal, infections.
Compositions and articles that can be used in the treatment of microbes such as bacteria remain desirable. Liquids that break down the EPS/EPCS macromolecular matrix or that bypass and/or disable the defenses inherent in therein, thereby permitting the liquid or a component thereof to access and kill the bacteria in a down-regulated state, are particularly desirable. Such a liquid that is lethally effective while having no or very limited toxicity is of significant interest and commercial value.
Methods and articles capable of treating bacteria that colonize acute wounds at the time of injury and during all stages of healing, as well as in the treatment of chronic wounds, also are highly desirable.
Also of significant interest are methods, compositions capable of treating and/or remedying any of a variety of oral and mucosal conditions associated with biofilms; preventing or remedying HAIs and/or biofilms in which the microorganisms can be entrained; preventing the growth of or removing biofilms from implantable (or implanted) devices and articles; and sterilizing or otherwise processing multiuse medical equipment.